Continuity mistake: When Bullock is warning Reeves of the coming winter blizzard, she is looking through pictures that depicted her and her friends enjoying the snow. She then turns to the dog and asks "Remember that day? You were not happy". However it's revealed that both characters have the same dog, given to Bullock's boyfriend by Reeves, so when the snow happened in Reeves' time - 2004 - the dog was with him.
Continuity mistake: During the opening credits, Kate leaves the Lake House via the kitchen, where we see the indoor tree is branches only-no leaves. Then from her car she looks back to the house, where we now see that tree is covered in orange leaves.
Continuity mistake: During the scene when Alex and Mona are riding in the truck with Jack the dog in the back end, the dog vanishes during several shots in which she should be visible.
Continuity mistake: In the lunch scene where Sandra is showing her mom the letter she says the year is 2006. The poster behind her is advertising tickets for the year 2004.
Continuity mistake: When Sandra Bullock is at the table in her mother's kitchen, she has her hand to her chin during a close-up, but when the camera angle changes, both hands are on the table.
Answer: The movie is not about them trying to find ways to meet. They are not trying that hard to meet and the time distance is a metaphor. I think the movie misses the tension that she is trepidatious about meeting and he is trying to respect that. He gets killed the first time for trying to force it! This shows when the stack of letters is piling away. She is worried he is a coward who will not be able to handle real romance. This is shown in his retreat to build mass produced houses and has something to do with his mom/dad. She's the doctor, he's the architect: she saves people for a living and is hung up about her own father's death. It's only when it's life or death that she gets over it and he also figures himself out and stops trying to fix everything.